Hi RG. It is a honeywell rth6500wf. Gas furnace
just switch back to an old HW mercury thermostat - furnace workign fine.
the old thermostat had a red and a white wire - connected the white to c and the red to r and kept the jump wire to rc
there are 2 unused wires a blue and a black - but they are not connected at the furnace end either (loose at both ends) - it looks like there are places they could go on furnace end
ok give me a minute. workign on it.